Identifying factors that contribute to mango resin canal discolouration

Abstract

Resin canal discolouration (RCD) is a quality defect that reduces the market value of ripe mango fruit. Market reports of RCD have increased during the past two mango seasons, particularly for early-season ‘Kensington Pride’ fruit produced near Darwin in the Northern Territory. A 1-year project was undertaken during the 2013 mango season to start identifying possible factors that contribute to RCD. The research focused on ‘Kensington Pride’ fruit produced in the Darwin production area. The research team monitored fruit from orchard to market, conducted specific trials, and completed detailed scientific evaluation of affected fruit. Preliminary findings suggest that RCD:
• Can also occasionally be found in green fruit on the tree or at grading but only when the fruit or stems have severe physical injury or pathogen infection.
• Occurrence can vary considerably between different orchards and for different harvest dates.
• Increases in severity as fruit develop from firm ripe to overripe.
• Incidence is higher in fruit that are exposed to commercial handling procedures than those ripened directly off the tree.
• Can be present in the flesh without symptoms being exhibited on the skin.
• Incidence can be higher in early-season fruit than those picked later.
• Incidence can be higher in fruit harvested soon after a rain event.
• Symptoms may be associated with bacterial infection.
The observations to-date suggest that RCD is likely to occur when field conditions result in the production of ‘sensitive’ fruit that, in turn, express the defect when exposed to the common harvest and postharvest stresses. Follow-on R&D will aim to confirm the causes of RCD and to develop reliable control measures.